Could someone please help me sort out my Garretts of Lonan?

Margaret Garrett married my ancestor Philip Cowin on 8 April 1843 at Lonan Parish. The certificate (page 31 f General Registry 1843) records Philip, 33 years, as a farmer in good circumstances with a father Thomas Cowin, and records Margaret, 20 years, as a farmer’s daughter with a father William Garrett.

I am having great trouble establishing the wider Garrett family, especially the mother and siblings of Margaret. The IGI has a Margaret Garrett born 10 August 1823 in Lezayre to William Garrett and Judith Killip. Despite Garretts being in Lonan for some generations, this is the best fit and many Garrett leads go back to Lezayre.

In Census 1841 (Lonan, District 2, Page 15, Grawe [?]) we find William Garrett (60, farmer), Judith Garrett (60), William Garrett (20), Margaret Garrett (15), Ann Garrett (20, female servant) and James Corlett (35, male servant). Is this a different family?

In Census 1851 at 2nd District, Grawe, Lonan, we find children Ann and Thomas Cowin with the Garrett family, William (b1785) and Judith (b 1781), and their son William Garrett age 30. The children are thought to be of daughter Ann Garrett (born 7.8.1814, died 20.7.1867) and William Cowin (baptized 9.1.1814, died 17.9.1868) married on 14 October 1837 at Lonan. William was a brother to Philip Cowin. All the Garretts were listed as coming from Lezayre.

Any assistance would be greatly appreciated. I can supply information on the Cowins and Garretts downunder if interested.